29Si Hyperfine Structure of the E'_\alpha Center in Amorphous Silicon Dioxide

We report a study by electron paramagnetic resonance (EPR) on the E'_\alpha point defect in amorphous silicon dioxide (a-SiO2). Our experiments were performed on gamma-ray irradiated oxygen-deficient materials and pointed out that the 29Si hyperfine structure of the E'_alpha consists in a pair of lines split by 49 mT. On the basis of the experimental results a microscopic model is proposed for the E'_alpha center, consisting in a hole trapped in an oxygen vacancy with the unpaired electron sp3 orbital pointing away from the vacancy in a back-projected configuration and interacting with an extra oxygen atom of the a-SiO2 matrix.Comment: 4 page

Sensing of transition metals by top-down carbon dots

Carbon quantum dots (CQDs) are a new class of carbon-rich materials with a range of unique optical and structural properties. They can be defined as carbon nanoparticles, with sizes in the range of 1–10 nm, displaying absorption and emission activities in the UV-VIS range. Depending on the structure, CQDs display a wide variability of properties, which provides the possibility of finely tuning them for several applications. The great advantages of CQDs are certainly the ease of synthesis, non-toxicity, and the strong interactions with the surrounding environment. Based on this, CQDs are especially promising as selective chemosensors. The present study reports on carbon quantum dots synthesized with a top-down (TD) approach, and characterized by different optical, spectroscopic, and morphological techniques to identify the selectivity for metal ions belonging to the first transition series. In particular, the study focuses on the interaction between two samples, namely TD and TDA, featuring different surface functionalization, and heavy metal ions. Their sensing towards Co2+, Cu2+, Fe3+, Zn2+, and Ni2+ has been tested by fluorescence (PL), steady state absorption spectroscopy, and time-resolved PL spectroscopy, in order to determine the fluorescence quenching. We found a PL quenching in the presence of concentrations of metal salts starting from 0.5 µM, and a selectivity towards the interacting ions, depending on CQDs’ surface features paving the way for their use for sensing

Investigation by raman spectroscopy of the decomposition process of HKUST-1 upon exposure to air

We report an experimental investigation by Raman spectroscopy of the decomposition process of Metal-Organic Framework (MOF) HKUST-1 upon exposure to air moisture (T=300 K, 70% relative humidity). The data collected here are compared with the indications obtained from a model of the process of decomposition of this material proposed in literature. In agreement with that model, the reported Raman measurements indicate that for exposure times longer than 20 days relevant irreversible processes take place, which are related to the occurrence of the hydrolysis of Cu-O bonds. These processes induce small but detectable variations of the peak positions and intensities of the main Raman bands of the material, which can be related to Cu-Cu, Cu-O, and O-C-O stretching modes. The critical analyses of these changes have permitted us to obtain a more detailed description of the process of decomposition taking place in HKUST-1 upon interaction with moisture. Furthermore, the reported Raman data give further strong support to the recently proposed model of decomposition of HKUST-1, contributing significantly to the development of a complete picture of the properties of this considerable deleterious effect

A comparative study of top-down and bottom-up carbon nanodots and their interaction with mercury ions

We report a study of carbon dots produced via bottom-up and top-down routes, carried out through a multi-technique approach based on steady-state fluorescence and absorption, time-resolved fluorescence spectroscopy, Raman spectroscopy, infrared spectroscopy, and atomic force microscopy. Our study focuses on a side-to-side comparison of the fundamental structural and optical properties of the two families of fluorescent nanoparticles, and on their interaction pathways with mercury ions, which we use as a probe of surface emissive chromophores. Comparison between the two families of carbon dots, and between carbon dots subjected to different functionalization procedures, readily identifies a few key structural and optical properties apparently common to all types of carbon dots, but also highlights some critical differences in the optical response and in the microscopic mechanism responsible of the fluorescence. The results also provide suggestions on the most likely interaction sites of mercury ions at the surface of carbon dots and reveal details on mercury-induced fluorescence quenching that can be practically exploited to optimize sensing applications of carbon dots

Performance Analysis of a Prototype High-Concentration Photovoltaic System Coupled to Silica Optical Fibers

High-concentration photovoltaic (HCPV) systems are one of the most promising technologies for the generation of renewable energy with high-conversion efficiency. Their development is still at an early stage, but the possibility of integrating high-concentration systems into buildings offers new opportunities to achieve the net-zero-energy building goal. Herein, the optical and energetic performance of a hybrid daylighting−HCPV prototype based on pure- or doped-silica optical fibers (OFs) to guide 2000× concentrated sunlight inside the buildings is evaluated. There, the light can either be used to illuminate interior spaces or projected on solar cells to generate electricity. The system equipped with a single 400 μm core-diameter OF is demonstrated to achieve a total efficiency of 15% and an optical efficiency of 45%

Delocalized Nature of the E'-delta Center in Amorphous Silicon Dioxide

We report an experimetal study by Electron Paramagnetic Resonance (EPR) of E'-delta point defect induced by gamma ray irradiation in amorphous SiO2. We obtained an estimetion of the intensity of the 10 mT doublet characterizing the EPR spectrum of such a defect arising from hyperfine interaction of the unpaired electron with a 29Si (I=1/2) nucleus. Moreover, determining the intensity ratio between this hyperfine doublet and the main resonance line of E'-delta center, we pointed out that unpaired electron wave function of this center is actually delocalized over four nearly equivalent silicon atoms.Comment: approved for publication in Physical Review Letter

MEDLAB Sicilia Le occasioni per l\u2019innovazione sociale e territoriale MEDLAB in Sicily An opportunity for social and territorial innovation

The volume contains written in italian and english language on the reflections and the final results of international partnership experience by Medlab (project promoted by European Commission, MED Program) concerning the case of Living Labs in Sicily. Gelardi and Salemi showed the action of the regional innovation instruments of urban and regional planning at institutional regional level and in particular the role of experience of international cooperation in the comparison of experiences of different kind of territorial innovation in the Euro-Mediterranean area. Marsh shows as the MedLab project has been to examine the current and potential role of Living Labs within regional development policy and the questions thrown up by considering Living Labs as a policy tool. This means looking at issues of development policy and linking their relevance to broader territorial innovation strategies. In addition, governance issues arise for coordinating different Living Lab initiatives within a territorial domain, with the aim of maximising benefits not only to ICT-based innovation and the local knowledge economy, but also to the fields of application that Living Labs address: the environment, the economy, social and government services, etc. The process has thus involved first looking at how these questions can be addressed from the standpoints of different types of actors and how they can engage in reciprocal learning processes. The idea is to develop a model of \u201cinnovation literacy\u201d for local authorities and policy makers, namely the capacity to structure the demand for and supply of ICT-based innovation in order to maximise the concrete benefits to specific policies and initiatives. The ultimate vision is of a virtuous circle whereby regional development authorities apply the Living Lab model in an increasing array of fields and the ICT industry increasingly recognises the value proposition of engaging in co-design processes in concrete local and regional development initiatives. In the following pages, we explore the experiences developed in the MedLab project according to three issues: a) a first exploration of the concept of \u201cterritorial innovation\u201d at the basis of the MedLab hypothesis, and its potential impact on policy and governance; b) The case story of the formation of the original TLL-Sicily partnership in 2007 and how that experience shaped the MedLab workplan; c) The summative conclusions of the MedLab project, exploring the concept of an emergent macro-regional Living Lab. Giambalvo e Lucido involved the analysis of urban change in a social and economic context particularly full of difficulties as the town of Favara. Their contribution tries to define the processes of social innovation when they born and move the first steps, this contribution aims to collect the challenge born inside the Medlab project \u2013 Mediterranean Living Lab for the Territorial Innovation to reflect on some of the outcomes of the Living Lab approach to support territorial innovation in the geographical areas of Sicily concerned by the pilot cases of MedLab (the spatial planning of the province of Ragusa and the strategic plan of the municipality of Favara). More specifically, the remark starts from a work of research on the field and facilitation of communicative processes aimed to identify what dynamics of social innovation, such as transactions among the social actors and what new micro-economic ecosystems are developing in the municipality of Favara, whose background has been explored and treated as territorial Living Lab. Di Bono e Parisi describe the way of the Province of Ragusa tried to initiate arrangements to create a Living Lab from experience of local planning and addressing to the involvement of the local firm to obtain a dinamic digital mapping of local creativity. In the contribution the autors try to show that the concept of innovation is still evolving and the market is not disappearing from this innovation concept, but it is one of its components; the social dimension is increasingly relevant, as well as the institutional innovation. In fact, public boards, dealing with the themes of territorial innovation, can re-design their role starting from networking open innovation approaches and building up public-private partnerships able to activate technological and social innovation processes in a participatory way. Trapani present a cotribution on theme about the report of launching a citizen initiative for the mobilization of the social capital in the second Constituency of Palermo; it includes the Brancaccio neighborhood very famous for the murder of Father Puglisi. The initiative is designed as an integrated program of architectural, urban, cultural, social, environmental and economic qualification for the development (also for touristic aims) of Castle Maredolce and (oncoming) park close the monument and the nearby gardens. The proposal which is maturing in this period, falls within the framework of infrastructural transformations taking place in the districts of Brancaccio and Bandita and compared to the new role of the metropolitan city in the new economies of the Mediterranean, namely in a context in which Sicily seems to remain more at the edge of Europe and see, in the cautious use of its cultural resources, a way of survival. The proposal initially moves from the definition of projects and visions for the architectural setting and the urban and social redefinition of a new square in front of an important Moorish Castle undergoing restoration. Furthermore, the interest is moved to the second municipal constituency. The integrated urban program consists of interventions which specify the contents of the strategic plan of Palermo for the second constituency. The urban part, specifically, is characterized by the presence of important infrastructure and services for the production of small and medium-sized enterprises. It has been possible to examine the characteristics of the citizens, their expectations in terms of their objectives and concerning the concrete possibilities of integrated planning and design within participatory and urban sphere on the background of the failure of urban traditional planning tools

Characterization of E'delta and triplet point defects in oxygen deficient amorphous silicon dioxide

We report an experimental study by electron paramagnetic resonance (EPR) of gamma ray irradiation induced point defects in oxygen deficient amorphous SiO2 materials. We have found that three intrinsic (E'gamma, E'delta and triplet) and one extrinsic ([AlO4]0) paramagnetic centers are induced. All the paramagnetic defects but E'gamma center are found to reach a concentration limit value for doses above 10^3 kGy, suggesting a generation process from precursors. Isochronal thermal treatments of a sample irradiated at 10^3 kGy have shown that for T>500 K the concentrations of E'gamma and E'delta centers increase concomitantly to the decrease of [AlO4]0. This occurrence speaks for an hole transfer process from [AlO4]0 centers to diamagnetic precursors of E' centers proving the positive charge state of the thermally induced E'gamma and E'delta centers and giving insight on the origin of E'gamma from an oxygen vacancy. A comparative study of the E'delta center and of the 10 mT doublet EPR signals on three distinct materials subjected to isochronal and isothermal treatments, has shown a quite general linear correlation between these two EPR signals. This result confirms the attribution of the 10 mT doublet to the hyperfine structure of the E'delta center, originating from the interaction of the unpaired electron with a nucleus of 29Si (I=1/2). Analogies between the microwave saturation properties of E'gamma and E'delta centers and between those of their hyperfine structures are found and suggest that the unpaired electron wave function involves similar Si sp3 hybrid orbitals; specifically, for the E'delta the unpaired electron is supposed to be delocalized over four such orbitals of four equivalent Si atoms.Comment: Approved for publication in Physical Review